Well, Constitutionally speaking, that is not so. The 3 branches of government were intended to be co-equal, with no one of them bowing to the other.
Well, constitutionally speaking, that IS so.
The legislature, representing “We, the People” determines, through the laws it passes, how the country is to be run.
The executive branch, headed by the Chief Magistrate (”president”) is charged with faithfully EXECUTING those laws.
The Chief Magistrate IS empowered by the Constitution to veto any law, but even that can be overridden by the legislature.
Theoretically, absent any laws from Congress, the executive branch has nothing to do.
Certainly there are necessary checks and balances between the branches, but that does not make them “co-equal”.